1. Field of the Invention
This invention relates to an overhead projector, in which characters, a picture and the like drawn on a transparent sheet rested on a horizontally supported member are projected onto a screen or the like, and more particularly to a conveniently portable overhead projector.
2. Description of the Prior Art
As well known, in a reflectory type overhead projector, a light source positioned upwardly of a mirror-Fresnel plate illuminates an object to be projected, which is disposed on the mirror-Fresnel plate, the light is reflected therefrom toward the light source, the reflected light is enlarged and projected onto a screen via a projecting lens, a direction changing mirror and the like. As described above, in the reflectory type overhead projector, the light source is positioned upwardly of the mirror-Fresnel plate similarly to a projection unit, whereby the thickness of the overhead projector downwardly from the mirror-Fresnel plate becomes small as compared with a transmission type overhead projector, in which the object to be projected is illuminated by the light source positioned downwardly of a Fresnel plate, so that the overhead projector is advantageously rendered compact in size. In consequence, in order to make the overhead projector portable, the reflectory type overhead projector should be adopted through the utilization of the aforesaid advantage.
Now, the above-described portable overhead projector should be rendered compact in size to be conveniently portable by adopting such an arrangement that a projection unit and supports are folded toward the mirror-Fresnel plate. However, if the supports, to which the projector unit is mounted, are folded before the folding of the projection unit, there is a possibility that the forward end portion of the projection unit upon the mirror-Fresnel plate to damage it.
Furthermore, in order to make the overhead projector portable, it is necessary that the overhead projector be housed in a portable case, which can be hung down by hand. With the overhead projector housed in the above-described portable case, the mirror-Fresnel plate is held horizontally through the utilization of an edge portion of the top surface of the case during projection.
In a construction for mounting the mirror-Fresnel plate to the overhead projector as described above, a space downwardly from the mirror-Fresnel plate in the case forms a dead space. In consequence, in housing the conventional overhead projector, the mirror-Fresnel plate is temporarily removed from the edge portion of the case, the projection unit, supports and the like are housed in the case, and thereafter, the mirror-Fresnel plate is placed on the overhead projector for housing it. To omit the aforesaid operation of removing the mirror-Fresnel plate, it may be possible to affix the mirror-Fresnel plate to the edge portion of the top surface of the case. However, such a fixation as described above results in that the aforesaid dead space is formed beneath the mirror-Fresnel plate and the case for housing itself becomes large in its volume, thus adversely affecting portability.